TWI743122B - System and method for generating neutrons - Google Patents

Abstract

The present disclosures relates to an ion beam assembly where a relatively small deflection angle (approximately 15° from the center of the beam line) is used in conjunction with two beam dumps located on either side of the beam. In some embodiments, the combination of the two beam dumps and the magnet assembly can provide an ion beam filter. In some embodiments, the resulting system provides a smaller, safer and more reliable ion beam. In some embodiments, the ion beam can be a proton beam.

Description

System and method for generating neutrons

This application claims the priority and rights of U.S. Provisional Patent Application No. 62/335,233 filed on May 12, 2016. The disclosure of the U.S. Provisional Patent Application is incorporated herein by reference in its entirety.

The present disclosure relates to a method and system for generating neutrons using a system with ion beam filters.

The ion beam generated by a particle accelerator or by other means can be used to generate neutrons by bombarding a neutron generation target with an ion beam. The generated neutrons can then be used in procedures such as Boron Neutron Capture Therapy (BNCT). However, in some systems, the ion beam or proton beam is high-power, and when it is not properly controlled, it may cause damage to the system that uses the ion beam or proton beam internally.

The present disclosure relates to an ion beam assembly in which a relatively small deflection angle (approximately 15° from the center of the beam line) is used in combination with two beam stacks located on either side of the beam. The combination of two beam stacks and magnet assembly can provide an ion beam filter. The resulting system provides a smaller, safer, and more reliable ion beam. In some embodiments, the ion beam may be a proton beam.

This disclosure relates to a system for generating neutrons. The system may have: an ion source configured to generate an ion beam; and a magnet system configured to deflect the ion beam from the center of the ion beam by a first angle. The system may have a rotating neutron source, the rotating neutron source is set at a first angle from the center of the beam, and is configured to receive the ion beam and generate a neutron flux. The system may have a first rotating beam stack configured to receive a first plurality of ions from an ion beam. The system may have a second rotating beam stack, the second rotating beam stack is set at a second angle from the center of the ion beam, and is configured to receive a second plurality of ions from the ion beam, wherein the second angle is greater than The first angle.

In some embodiments, the ion beam may be a proton beam, a deuterium beam, or a combination thereof.

In some embodiments, the first angle may be between 0 degrees and 45 degrees. In some embodiments, the first angle may be substantially 15 degrees.

In some embodiments, the first rotating beam stack and the rotating neutron source may have internal cooling channels for water cooling.

In some embodiments, the first rotating beam stack may be graphite, aluminum, or a combination thereof. In some embodiments, the second rotating beam stack may be graphite. In some embodiments, the rotating neutron source may be lithium.

In some embodiments, the first rotating beam stack may have one or more openings, and the first beam detector may be disposed behind the first rotating beam stack to monitor the contour of the ion beam. In some embodiments, the rotating neutron source may have one or more openings, and the second beam detector may be arranged behind the rotating neutron source to monitor the profile of the ion beam.

In some embodiments, the first rotating beam stack may be arranged on the straight path of the ion beam.

The present disclosure also relates to a method for generating neutrons. The method may include: generating an ion beam by an ion source, and deflecting the ion beam from the center of the ion beam by a first angle by a magnet system. The method may include receiving an ion beam, and generating a neutron flux by a neutron source disposed at a first angle from the center of the ion beam. The method may include receiving the first plurality of ions from the ion beam by the first rotating beam stack. The method may include receiving a second plurality of ions from the ion beam by a second rotating beam stack disposed at a second angle from the center of the ion beam, wherein the second angle is greater than the first angle.

In some embodiments, the method may include generating a proton beam, a deuterium beam, or a combination thereof as an ion beam.

In some embodiments, the first angle may be between 0 degrees and 45 degrees. In some embodiments, the first angle may be substantially 15 degrees.

In some embodiments, the method may include cooling the first rotating beam stack and the rotating neutron source by passing water through internal cooling channels in the first rotating beam stack and the rotating neutron source.

In some embodiments, the first rotating beam stack may be graphite, aluminum, or a combination thereof. In some embodiments, the second rotating beam stack may be graphite. In some embodiments, the rotating neutron source may be lithium.

In some embodiments, the method may include passing the ion beam through one or more openings on the first rotating beam stack, and receiving the ion beam by a first beam detector behind the first rotating beam stack, To monitor the profile of the ion beam. In some embodiments, the method may include passing the ion beam One or more openings on the rotating neutron source, and the ion beam is received by a second beam detector behind the rotating neutron source to monitor the contour of the ion beam.

In some embodiments, the method may include: arranging the first rotating beam stack on the through path of the ion beam.

100, 200: beam delivery system

102, 202: ion beam/beam

104: (deflector) magnet system / deflector magnet

106: Proton Beam

108: (rotating) lithium target

110: beam trajectory

112: H ₂ ⁺ beam/bundle stack

114: Rotating Bundle

204: Magnet System

208: Rotating Lithium Target/Lithium Target Disc

210: (beam) trajectory

212: H ₂ ⁺ beam / H ₂ ⁺ position

214: (First) Rotating Bundle/(First) Bundle

215: (Second) Rotating Bundle/(Second) Bundle

216: Proton

218: ``Straight-through'' (beam tuning) position

When considered in conjunction with the following drawings, referring to the following detailed description of the disclosed subject matter, various purposes, features, and advantages of the disclosed subject matter can be more fully understood, wherein similar reference numbers identify similar elements.

FIG. 1 shows a schematic diagram of a beam delivery system based on 90° magnetic beam deflection according to some embodiments of the present disclosure.

2 shows a schematic diagram of a beam delivery system based on 15° deflection/analysis of beams generated from an accelerator according to some embodiments of the present disclosure.

In the following description, many specific details about the system and method of the disclosed subject matter and the environment in which such system, method, and medium can be operated are explained in order to provide a thorough understanding of the subject matter disclosed. However, those familiar with the art will understand that the disclosed subject matter can be practiced without such specific details, and will understand that certain features well known in the art will not be described in detail in order to avoid complicating the disclosed subject matter change. In addition, it will be understood that the examples provided below are exemplary, and it will be understood that other systems and methods within the scope of the disclosed subject matter can be envisaged.

The described neutron generator is based on the ⁷ Li(p,n) ⁷ Be reaction. When a proton beam with an energy range between 1.882 MeV (reaction limit) and about 2.6 MeV collides with a lithium target, neutrons are generated. The target is surrounded by a neutron energy moderator, which eliminates the high-energy neutrons generated in the reaction and results in a typical neutron energy spectrum in the range of 0.5 eV to 10 keV. These superthermal neutrons are very suitable for BNCT.

High-energy protons can be produced using a number of accelerator technologies, including but not limited to electrostatic ("single-ended" or "tandem"), linear accelerators, radio frequency quadrupoles, and cyclotrons. Some accelerator architectures can generate high-power (~100kW), high-current (~40mA) proton beams dedicated to BNCT. These accelerators can use lithium target technology capable of manipulating high-power (~100kW) proton beams (see U.S. Application No. 15/147,565 filed on May 5, 2016, titled "Boron Neutron Capture Therapy Neutron Target for Boron Neutron Capture Therapy", which is incorporated herein by reference in its entirety) is used.

There may be several technical challenges in delivering this high-power beam from the accelerator to the lithium target, as discussed below.

First, the ion beam generated from a proton accelerator usually contains undesired ion species other than protons, which do not contribute to the generation of neutrons. These may include unfiltered ions such as H ₂ ⁺ , H ₃ ⁺ , N ⁺ , O ⁺ , OH ⁺ and the like generated in the ion source. These undesired ions may be generated as secondary ions when the main beam collides with the remaining gas atoms or molecules in the accelerator tube, and they may also be accelerated toward the target.

Ion beams containing ions of different mass or energy can be easily filtered by passing the beam through a sector magnet. This technique is used in both isotope separator and mass spectrometer systems, and utilizes the fact that the radius of curvature of ions traversing the magnetic field depends on the magnetic field according to the following equation: R α H ^-1 e ^-1 E ^1/2 M ^1/2 Where R is the radius of curvature, H is the magnetic field, e is the charge on the ion, M is the ion mass, and E is the ion energy.

For a given deflection geometry, by adjusting the magnetic field to an appropriate value, the required ion species can be easily selected and guided to the target.

In the case of a high power ~100kW beam, it should be noted that even a small undesired part of the main beam can have significant power and can cause damage to the beam steering system. _{For example, the portion of H 2} ⁺ ions generated from the ion source can usually be ~10% of the total beam output, and will result in a beam power of ~10kW after acceleration.

Second, if the high-voltage part of the accelerator is disturbed by the arc in the accelerator tube or high-voltage insulation structure, the energy of the proton beam may be temporarily reduced, and the beam may be deflected with a smaller radius, thereby guiding the beam away from its fan-shaped The expected path in the magnet. In this case, the beam may hit areas of the system that cannot be manipulated with high power. The "structure" here can refer to any part of the high-voltage equipment (accelerator line) except the tube (it is only the accelerator electrode and the intervening insulator, and the vacuum and pressurized sulfur hexafluoride ("SF6") gas Separate air-tight enclosure). Therefore, the structure may include power supply, drive shaft, alternator, and any structural elements that physically support these objects. In some embodiments, the structure can be immersed in SF6.

Third, one or more operator errors in the control system may accidentally mislead the beam into the vulnerable area of the system.

Fourth, the ability to add neutron absorbing materials (such as concrete) to prevent the direct "line of sight" between the neutrons that generate lithium on the target and the proton accelerator is another requirement of the beam delivery system. This will be significantly more difficult to achieve with a conveyor system that has no bends in its beam.

Figure 1 shows a simple schematic diagram of a beam delivery system 100 based on 90° magnetic beam deflection. In some embodiments, during operation, the beam delivery system 100 may include an ion beam 102 from an accelerator, a magnet system 104, a proton beam 106, a rotating lithium target 108, and a rotating beam stack 114. Figure 1 also shows a typical beam trajectory 110 and H ₂ ⁺ beam 112 during a high voltage arc. The whole system can be installed in the vacuum chamber.

In the normal operating sequence, first, with the deflector magnet system 104 closed, the beam 102 is tuned to the desired intensity at the through-type beam stack 112. Then, the deflector (analyzer) magnet 104 is turned on to guide the proton beam toward the lithium target 108 at 90 degrees in this example. In some embodiments, the ion source can be turned off during this process, commonly referred to as beam sweeping, to prevent damage to the walls of the vacuum chamber.

Figure 2 shows a simple schematic diagram of a beam delivery system 200 based on 15° deflection/analysis of the beam generated from the accelerator. The beam delivery system 200 shown in FIG. 2 may include an ion beam 202, a magnet system 204, a rotating lithium target 208, a first rotating beam stack 214, and a second rotating beam stack 215. Figure 2 also shows a typical beam trajectory 210 and H ₂ ⁺ beam 212 during a high voltage arc. The first rotating beam stack 214 shows both the "through" beam tuning position 218 and the H ₂ ⁺ position 212 during operation. The second rotating beam stack 215 shows two typical beam trajectories 210 that represent two different degrees of voltage collapse during the arc. These trajectories 210 represent the typical high-power beam range that may exist during the arc. The beam angle may be slightly greater than 15°, but it may be difficult to maintain the desired optical properties (for example, no beam waist). The beam angle can be slightly less than 15, but it becomes more difficult to avoid the line of sight from the target to the accelerator.

As shown in Figure 2, in some embodiments, two rotating beam stacks 214, 215 have been added. The first beam stack 214 can be used to tune the system in the "through" position 218 when the deflector magnet is closed, and the first beam stack 214 is designed to manipulate the full beam power. The first beam stack 214 can also be used to collect the H ₂ ⁺ beam 212 and any additional heavy ion contaminants during normal operation. The second beam stack 215 can collect any beams with a deflection greater than 15°, and these beams can occur during the voltage collapse of one or more of the high voltage supplies in the accelerator. In some embodiments, the first rotating beam stack 214 may have a similar diameter to the rotating lithium target 208. In some embodiments, the first rotating beam stack 214 may have a larger diameter than the rotating lithium target 208. In some embodiments, the second rotating beam stack 215 may have a much smaller diameter than the first beam stack 214 and the rotating lithium target 208. In one embodiment, the rotating lithium target 208, the first rotating beam stack 214, and the second rotating beam stack 215 may have diameters of 1.2 m, 1.5 m, and 0.6 m, respectively.

These bundles 214, 215 can be water-cooled rotating disks, such as the U.S. Application No. 15/147,565 filed on May 5, 2016, titled "Neutron Targets for Boron Neutron Capture Therapy (Neutron Target for Boron Neutron Capture Therapy) used in the lithium target described in ", the case is incorporated herein by reference in its entirety. In some embodiments, graphite plates can be used, which can be irradiated by radiation to the water-cooled walls of the vacuum chamber Consumption of scattered beam power. In some embodiments, the second rotating beam stack 215 may be a graphite plate cooled by radiation cooling, and the first rotating beam stack 214 and the rotating lithium target 208 may have internal cooling channels for water cooling . In some embodiments, the first rotating beam stack 214 may have a different configuration (ie, the shape and number of cooling channels, petals, diameter, and material) compared to the rotating lithium target 208. In some embodiments, the first rotating beam stack 214 may have an array of openings, and the first beam detector may be disposed behind the first rotating beam stack 214 so that the outline of the ion source can be determined. In some embodiments, the rotating lithium target 208 may include an array of openings, and the second beam detector may be disposed behind the rotating neutron source, so that the outline of the ion source can be determined.

The first rotating beam stack 214 may include materials selected to limit gamma and neutron radiation hazards caused by the full power beam impact on the first rotating beam stack 214 and normal The impact of the filtered molecular beam on the first rotating beam stack 214 during operation is generated. In some embodiments, if the ion source is a proton beam, the first rotating beam stack 214 may be graphite. In some embodiments, if the ion source is a deuterium beam, the first rotating beam stack 214 may be aluminum.

From the configuration shown in Figure 2, it can be seen that the high-power beam 202 (~100kW) from the accelerator can be safely contained during operation. One or more beams may only hit the lithium target disk 208 or the first rotating beam stack 214 designed to manipulate the full beam power.

Finally, it should be noted that the magnetic deflection angle avoids the direct line of sight from the Li target area to the accelerator. This architecture empowers neutron radiation shielding (coagulation The strategic placement of soil blocks, plastic, steel, lead, etc.) in order to prevent the problem of neutron radiation damage to the accelerator.

The described system can have the following advantages: (1) a smaller (due to smaller angle) and simpler magnet; (2) a more convenient linear layout for facility design; and (3) the beam stack can also be used as a radiation The beam limiting aperture functions to precisely define the area on the main target that the beam may hit. This third advantage can prevent any stray scattered beams from reaching unprotected areas of the system. Compared to large-angle systems that include dedicated bundles for this purpose, fewer bundles are required in the case of small angles.

The described system can also result in improved beam optics; in particular, a 15° deflector can eliminate the need for a waist in the beam. The waist in the beam line is where the beam crosses over itself and thus becomes highly focused. The presence of the waist is a hazard to the adjacent beamline structure and the main target. For this reason, due to instability, magnet failure, operator error, or other abnormal environments, the waist may be accidentally guided to components further downstream of the wire harness. In the absence of a 15° beam harness at the waist, the possibility of this failure mode is greatly reduced.

Therefore, the features of the disclosed subject matter are summarized in order to better understand its subsequent detailed description and to better understand the contribution of the disclosed subject matter to the prior art.

In this regard, before explaining in detail at least one embodiment of the disclosed subject matter, it should be understood that the disclosed subject matter is not limited to its application to the configuration details and component configuration described in the following description or illustrated in the drawings. The disclosed subject matter can have other embodiments and be practiced and implemented in a variety of ways. Shi. In addition, it should be understood that the terms and terms used herein are for descriptive purposes and should not be regarded as limiting.

Therefore, those familiar with the art will understand that the concepts on which the present disclosure is based can be easily used as a basis for designing and implementing other structures, methods, and systems for some purposes of the disclosed subject matter.

Although the disclosed subject matter has been described and exemplified in the foregoing exemplary embodiments, it should be understood that the present disclosure has been made by way of example only, and can be made without departing from the spirit and scope of the disclosed subject matter Many changes in the details of the implementation plan of the disclosed subject matter.

200: beam delivery system

202: ion beam/beam

204: Magnet System

208: Rotating Lithium Target/Lithium Target Disc

210: (beam) trajectory

212: H ₂ ⁺ beam / H ₂ ⁺ position

214: (First) Rotating Bundle/(First) Bundle

215: (Second) Rotating Bundle/(Second) Bundle

216: Proton

218: ``Straight-through'' (beam tuning) position

Claims (22)

A system for generating neutrons, the system comprising: an ion source configured to generate an ion beam; a magnet system configured to deflect the ion beam from the center of the ion beam by a first Angle; a rotating neutron source, which is set at the first angle from the center of the ion beam, and is configured to receive the ion beam and generate a neutron flux; a first rotating beam stack , Which is assembled from the ion beam to receive a first plurality of ions; and a second rotating beam stack, which is arranged at a second angle from the center of the ion beam, and which is assembled from the The ion beam receives a second plurality of ions, wherein the second angle is greater than the first angle. The system of claim 1, wherein the ion beam comprises a proton beam, a deuterium beam, or a combination thereof. Such as the system of claim 1, wherein the first angle is between 0 degrees and 45 degrees. Such as the system of claim 3, wherein the first angle is substantially 15 degrees. The system of claim 1, wherein the first rotating beam stack and the rotating neutron source include internal cooling channels for water cooling. The system of claim 1, wherein the first rotating beam stack comprises graphite, aluminum, or a combination thereof. Such as the system of claim 1, wherein the second rotating beam stack contains graphite. Such as the system of claim 1, wherein the rotating neutron source contains lithium. The system of claim 1, further comprising: one or more openings located on the first rotating beam stack, and a first beam located behind the first rotating beam stack for monitoring a profile of the ion beam Beam detector. The system of claim 1, further comprising: one or more openings located on the rotating neutron source, and a second beam detector located behind the rotating neutron source for monitoring a profile of the ion beam . Such as the system of claim 1, wherein the first rotating beam set is arranged on a straight path of the ion beam. A method for generating neutrons, the method comprising: generating an ion beam by an ion source; deflecting the ion beam from the center of the ion beam by a first angle by a magnet system; receiving the ion beam, and A neutron flux is generated by a rotating neutron source disposed at the first angle from the center of the ion beam; a first plurality of neutron fluxes are received from the ion beam by a first rotating beam stack Ions; and receiving a second plurality of ions from the ion beam by a second rotating beam stack disposed at a second angle from the center of the ion beam, wherein the second angle is greater than the first angle. The method of claim 12, further comprising: generating a proton beam, a deuterium beam, or a combination thereof as the ion beam. Such as the method of claim 12, wherein the first angle is between 0 degrees and 45 degrees. Such as the method of claim 14, wherein the first angle is substantially 15 degrees. The method of claim 12, further comprising: cooling the first rotating beam stack and the rotating neutron source by passing water through internal cooling channels in the first rotating beam stack and the rotating neutron source . The method of claim 12, wherein the first rotating beam stack comprises graphite, aluminum, or a combination thereof. The method of claim 12, wherein the second rotating beam stack contains graphite. The method of claim 12, wherein the rotating neutron source contains lithium. The method of claim 12, further comprising: passing the ion beam through one or more openings on the first rotating beam stack; and using a first beam detector behind the first rotating beam stack The ion beam is received to monitor a profile of the ion beam. The method of claim 12, further comprising: passing the ion beam through one or more openings on the rotating neutron source; and receiving the ion beam by a second beam detector behind the rotating neutron source To monitor the profile of one of the ion beams. Such as the method of claim 12, which further comprises: arranging the first rotating beam stack on a straight path of the ion beam.

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